Boston lawyer who has specialized in helping Catholic leaders reach speedy and amicable agreements with victims of clergy sexual abuse has been hired by the incoming leader of the Archdiocese of Boston, Bishop Sean Patrick O'Malley, to help speed the settlement of more than 500 pending lawsuits.

Thomas H. Hannigan Jr. said yesterday that he will attend a closed-door conference this morning between lawyers in the case and Superior Court Judge Constance M. Sweeney. Hannigan said that, for now, he will serve in an advisory capacity to O'Malley, who is set to be installed as archbishop July 30.

''Bishop O'Malley has asked me to be his personal source of information in the case,'' Hannigan said during an interview last night. ''He has asked me to assess where things are presently and to give him advice on how to resolve this.''

Hannigan, a lawyer with the Boston firm of Ropes & Gray, has been praised by colleagues and opponents as a low-key, thoughtful lawyer who focuses on the big picture. He worked with O'Malley in Fall River in the early 1990s to settle 101 lawsuits filed by the victims of now defrocked priest James R. Porter, and represented the Jesuits last year, settling abuse claims filed by 15 former students at Boston College High School.

Hannigan declined to comment yesterday on whether his role representing the church would broaden, even though lawyers involved in the case contend that he will assume a lead role after O'Malley's installation as archbishop. ''No decisions have been made yet,'' Hannigan said.

The Rev. Christopher Coyne, a church spokesman, said yesterday that the longtime attorney for the archdiocese, Wilson D. Rogers Jr., remains the lead attorney.

''There is currently no change in the legal representation of the archdiocese,'' Coyne said.

The official statements aside, a lawyer who has worked with Hannigan said his appearance is a sign that Hannigan will formally supplant Rogers as the lead attorney after O'Malley's installation. Rogers did not return calls yesterday.

The lawyer, who spoke on the condition that he not be identified, said Hannigan will have behind him the resources of a major law firm, instead of the small family firm currently representing the church that has appeared to struggle at times with the sheer volume of litigation.

Even though Hannigan will not have a formal role for the time being, the lawyer added, ''he will be the elephant in the courtroom'' when Sweeney meets with both sides this morning.

The archdiocese is currently being represented by longtime church attorney Rogers and his son, Wilson D. Rogers III, whose handling of the abuse claims has been criticized by alleged victims and their lawyers.

The Rogerses' firm opened the archdiocese up to criticism by pursuing hardball legal tactics against victims, yet declined to use those same tactics against the church's uncooperative insurance companies, despite being advised to do so by attorneys for victims and a lawyer representing Cardinal Bernard F. Law.

In contrast, when Hannigan worked for O'Malley in Fall River in the early 1990s, the diocese borrowed money to pay at least $8 million in abuse claims, and then sued insurance giant CNA to recover the funds.

Numerous attorneys and others who have worked with Hannigan, 51, of Needham called him the right lawyer if O'Malley, as he has pledged, wants a speedy and fair settlement to the more than 500 outstanding claims.

''He is the most honest, principled, fair-minded man that I know,'' said John M. Hession, a lawyer with the Boston firm McDermott, Will & Emery who was Hannigan's roommate at the University of Notre Dame in the 1970s. ''The guy is a mensch among men.''

Paul Kelly, a fellow Needham resident and Boston lawyer who also worked at Ropes & Gray, called Hannigan a good choice to deal with a case where plaintiffs' emotions have run high.

''He's one of these guys who doesn't have a big ego,'' said Kelly, a partner in the firm Kelly, Libby & Hoopes. ''He's a good, quality lawyer who would make an outstanding diplomat.''

Hannigan, the son of an FBI agent, graduated from Notre Dame in 1974 with a degree in chemical engineering and received his law degree from Boston College Law School in 1979. He is married with three children.